Data storage systems



Nov. 6, 1962 R. BIRD ETAL 3,063,042

DATA STORAGE SYSTEMS Original Filed Dec. 1, 1954 MATR\X flecomms CLOCKTRACK 4READiNG "I HEADS CLOCK I TRMN macommcak ISIJ/ A R X CLDCKTRACKISI?) /5/// 4 FIG. 2.

' INVENTORS ATTORNEYS United States Patent (Him DATA STORAGE SYSTEMSRaymond Bird and John Robert Cartwright, Letchworth,

England, assignors to International Computers and Tabulators Limited,London, England Original application Dec. 1, 1954, Ser. No. 472,453, now

Patent No. 2,958,856, dated Nov. 1, 1960. Divided and this applicationMay 17, 1960, Ser. No. 29,616

9 Claims. (Cl. 340-1741) This invention relates to data storage systemsusing a rotating member, such as adrum or disc, which has a magnetisablesurface.

This is a division of application Serial No. 472,453, filed December 1,1954, now Patent No. 2,958,856, entitled Magnetic Data Storage Systemsand assigned to the assignee of the present invention.

It is well known to employ a magnetic drum or disc for data storageincomputing machines and similar applications. around the rperiphery,each track containing several words or items of data. A clock track isusually provided to generate timing signals corresponding toeach pulseposition of each word, for gating signals for both reading and writingon the drum. In order to select a particular position on the drum forreading or writing, ithas been the practice to use a combinationnofspace selection, and time selection. The space selection-consists inselecting the head associated with the track containing the particularword position. This selection may be performed by a switching network ofrelay contacts or valves alone, or such a network acting in conjunctionwith a physical movement of a limited number of heads. The timeselection is performed by making the selected head operative toread or,write, as the case may be, at some selected interval after a referencepoint on the drum passes the selected head. This has been done,for-"example, byproviding an end of revolution pulse and an end of wordpulse, counting the end of word pulses, and determining coincidencebetween the counter and the number of the particular word position.

It is the object of the presentinvention to provide a simplified methodfor the selection of a desired word position on a magnetic drum or discstoragedevice, having a plurality of tracks, each containing a pluralityof words.

' According to the invention data storage apparatus mcludes a rotatablemagnetic storagemember with a data storage track providing a pluralityof word storage areas, a=transducing head cooperating with, thedata-track, signal gating means for the, transducing head, a clock pulsetrack on thegstorage member divided intov wordv areas correspondingtosaid ,word storage areas, a group of clock pulse signals recorded in atleast one of said clock pulse word areas and others of the clock pulsewordareas being blank, aplurality of reading heads spaced apart at wordintervals along the clock pulse track and cooperating with said recordedclock pulse signals to generate a train of clock pulses foreach wordstorage position, and switch-- ing means'interconnecting said pluralityof reading heads and said gating means and settable to apply to thegating means thatclock pulse train which corresponds to a selected one}of said word storage areas.

The invention will now be ample, with reference to the which:

FIGURE 1 is a schematic block diagram of one embodiment of theinvention; I

- FIGURE'la is a schematic illustration of a clock track and .theassociated reading heads;

j FIGURE 2 is a schematic block diagram of another and r embodiment, ofj the invention,

The data-is recorded in, a plurality of tracks described, by way of ex-,accompanying drawing, in

, thirty-two digit positions of the 1. of the drum 1,

3,063,042 Patented Nov. 6, 1 962 of the embodiment of FIGURE 2.

By way of illustration, quired to read out a selected word from dataalready recorded on a magnetic There are thirty-two data tracks fromwhich data may be readby thirty-two reading heads 2(1) to 2(32), ofwhich four heads are shown. Each track contains sixteen word recordingareas, each of which contains thirty-two binary digits.

' The word to be selected is that word which is recorded in thethirty-first track sensed by head 2(31) and which is recorded in thesecond word reference point on the magnetic drum 1.

- The first selection selecting the head 2(31). This is effected by aswitching 7. The switching matrix on five lines 5 which are tion toselect anyone matrix ,may consist of a network of the contactsofrelayscontrolled by. the lines 5- orof diodes fdr'fmulti-el'e'ctrode'valves,-according to other circuit. requirements, such as the maximumspeed at" which the matrix has to be switched. Switching matrices. of?this .lg eneral type are well knowm'and are described '-for example vin.a paper entitled Rect ifier Networks for"Multi Positi0n SWitch-,ingflby D.- R. Brown and N. Rochester'appearing at pages 139 to 147 ofVOl. 37,INO 2 of Proc. I.R.E. (February.,1 949). v p

A clock track 10 is provided on the drum 1 and sixteen clock trackreading heads 8 are arranged adjacent to this track circumferentiallyaround the drum 1,'the heads being spaced at one word intervals. Asingle group 9 (FIG, =1a) of thirty-two clock pulses is recorded on theclock track at such a position that it is being read by the head 8 (1)at the same time as the first word of each data track is being read bythe corresponding head 2.

Since the heads 8 are spaced apart at one word intervals, it followsthat the head 8(1) will produce a train of thirty-two clock pulsesignals coincident with the 'first word in each. data track, the head8(2) ,will produce a train of thirty-two clock pulse signals coincidentwith the second word, and so on. The single group 9 of recorded clockpulses will be read in turn byallthe heads 8 during one revolution sothat sixteen trains of clock pulses are generated, corresponding tothesixteen word positions in adatatra'ck. I

The output signals from the heads 8 are fed to a switching matrix11,.which is similar tothe matrix 4 except is controlled by thepotentials energised singly or in combinathat only four control lines12are needed to effect selec-- tion of any one of the sixteen heads.

the matrix 11 is fed to a which also receives the The output from gatingand amplifying circuit 6, output from the matrix 4 over Speed ComputingDevices," Hill Book Company in 1950. p

. summarising the operation of reading out a selected word from aselected data track,

published by the McGraw- 5 energised so that the required one of theheads 2 is sek the heads t; to appear on example, the matrix 4 willlected by the matrix 4 to read out signals to the line 7. Atthe sametime, the lines 12 are selectively energised to allow the clock pulsetrain from the required one of the line 13. In the present head 2(31) tothe line 7, and the matrix 11 will be-operated to connect the head 8(2)to the line 13. Thus, all

the data signals sensed serially by the head 2(31) will; be fed tothecircuit 6, via

the line 7, but the head 8(2) it will be assumed that it is re storagedrum 1 (FIGURE 1).

area starting from a given operation is, therefore, that of of thethirty-two heads. The

the lines 5 are selectively be operated to connect the will feed clockpulse signals to that circuit only during the time that the second wordis being sensed from the data track. Consequently, only the data signalsforming the second word will appear on output line 14 of the circuit 6.

If the words are very closely spaced along the tracks, it may not bepossible to mount the heads 8 sufficiently close together to provide therequired one word spacing. In this case two clock tracks may be used,each having one word recorded thereon, and the heads are then mounted sothat the heads 8(1), 8(3), 8(5) etc., read one clock track and the heads8(2), 8(4), 8(6) etc. read the other clock track.

In the embodiment of the invention shown in FIGURE 2, a single clocktrack is used, and this track is read by four heads 15(1), 15(2), 15(3)and 15 (4) arranged circumferentially around the drum 1, with the headsspaced at one word intervals. A pattern of clock pulse word groups 9(FIGURE 2a) is recorded on the clock track such that for each data wordposition a different combination of clock track heads is reading a wordgroup. One example of such a pattern is shown below. An X indicatingthat a word is recorded in that position. Data word positlon. 1 2 3 4 56 7 8 9 10 11 12 13 14 15 16 Clockword group X X X X X X X X Using thispattern, the data word positions at which each clock pulse head read aword group is shown below, and it will be seen that a unique combinationof heads are utilised for each of the sixteen positions.

1 2 3 4 5 6 7 8 910111213141516 XX XX 12 now control a matrix 16 whichswitches the four heads to one of two sets of output lines 17 and 18,depending upon whether the head is inoperative or operative for the dataWord position required. The matrix 16 is of known kind and is disclosedin the abovementioned paper Rectifier Networks for MultipositionSwitching. For example, for the ninth word position, the heads 15(1) and15(3) are connected to the first and third output lines 18 and the heads15(2) and 15(4) are connected to the second and fourth output lines 17.

The lines 17, 18 which are not connected to the heads are connected to aconstant voltage. The lines 17, 18 are connected to a circuit, thefunction of which is to gate to the circuit 6 on line 19 clock pulsesonly during the word position selected by the setting of matrix 16. Thiscircuit embodies a number of switching elements illustrated on page 12of Synthesis of Electronic Computing and Control Circuits published byHarvard University Press and represented by the same reference letters TC P used on that page. Thus the lines 18 are connected to four Tswitching elements 20 having a common output circuit as illustrated atthe sixth line of page 12 of the before-mentioned book, and forming afour-input and gate.

Each element 20 which is not connected to a head by matrix 16 isswitched on by the constant voltage. An output pulse will therefore beemitted, when and only when pulses are received simultaneously on thelines 18 which are connected to heads.

The lines 17 are connected in pairs to two two-input gates 21, theoutput from which are commoned and A.C. coupled through an inverter 22to a two-input and gate 23. The output from gate 20 is also applied togate 23 and the output on gate 23 is applied on line 19 to the device14.

Inverter 22 normally provides a priming voltage for The lines gate 23 sothat if a pulse is emitted by gate 20 there will;

be an output on line 19.

However, the occurrence of a pulse on any line 17 connected by thematrix 16 to a head will cause a pulse to pass to the inverter 22 andwill prohibit an output from gate 23. As an example, suppose the matrix16 is set for the ninth word position; clock pulses will then only bepassed by gate 23 when simultaneously there are pulses on the first andthird lines 18, so as to operate gate 20, and when there are no pulseson the second and fourth lines 17 so that no pulse is emitted by gates21. From an examination of the table it will be seen that thesecircumstances occur only during the ninth data word position.

The circuit of FIGURE 2 will not give clock pulses for the sixteenthword position since, as the table shows, no heads are connected to lines18.

If it is essential to use the sixteenth word position, this may bearranged by providing a second clock track having words of thirty-twopulses recorded in all the sixteen positions. The circuit associatedwith lines 18 is modified to provide a control voltage except when ahead connected to it is inoperative or the circuit associated with lines17 is operative. This control voltage is applied to a gate which alsoreceives pulses from the head reading the second clock track. The outputof this gate is fed to the circuit 6 instead of the output from thecircuit associated with lines 18.

It will be appreciated that the arrangements described are equallyapplicable to recording on the drum in a chosen word position if thecircuit 6 is modified so that a pulse applied to the line 14'produces anoutput on the line 7 if this pulse coincides with a clock pulse on theline 13, or the line 19.

With the arrangement of FIGURE 2, other patterns of clock pulse wordsmay be used with the heads in the relation shown, and the heads may alsobe spaced at other multiples of a word interval. The only requirement isthat the heads must provide a unique coding of outputs for each dataword position which is to be selected.

It will be appreciated that the arrangement of the clock tracks for eachform of the invention is depend ent solely upon the number of wordpositions in a data track and the number of digits in quently, the clocktracks need not berecorded on the drum itself; instead they may take theform of "phonic wheel pulse generators, mounted on the same shaft as thedrum, and associated with suitable pick-up or reading heads.Alternatively, a disc with alternate transparent and opaque sections maybe mounted on the drum shaft and sensed photo-electrically to producethe required clock pulse trains.

It has been explained how the selection of one data transducing head andone clock track reading head enables a selected data word to be readout. It will be apparent that neither selection involves the use ofcircuits which have to operate synchronously with the clock pulsetiming, so that the selection circuits can work at relatively slow speedand the switching matrices may be controlled by signals which are notsynchronous with the rotation of the drum.

We claim:

1. Data storage apparatus including a rotatable magnetic storage memberwith a data storage track providing a plurality of'word storage areas; atransducing head cooperating with all the storage areas of the datatrack; signal gating means for the transducing head;- a 'clock pulsetrack on the storage member divided into Word areas corresponding tosaid word storage area's,-

a group of clock pulse signals being recorded in at least one of saidclock pulse word areas and others of the clock pulse word areas beingblank; 'a plurality of-read-' ing head-s spaced apart at word intervalsalong-the clock pulse track andcooperating with said recorded clockpulse signals to generate trainsof clock pulses corresponding to' theword storage areas; word selecting static switching meansinterconnecting said plurality of reading heads and said gating means;and means for applying to the switching means address signals repeachword. Conseresenting a required word. storage area, said switchingmeans'operating in response to the application 'of'said address signalsto apply to the gat'ing means only that clock pulse trainwhichcorrsponds. to said-required word storage area, said gating meansthen being opened in response to the applied clock pulse train onlywhile said transducing head is cooperating with" said required wordstorage area.

. 2. Data storage apparatus comprising a multi-track, multi-wordrotatable first magnetic storage means having a plurality of paralleldata tracks, each track containing a plurality of successive wordstorage areas, a transducing head for each said data track for seriallytransducing signals corresponding to said successive word storage areason the respective tracks, track selecting means for rendering operativeone of said transducing heads, second magnetic storage meanssynchronously rotatable with said first storage means and havingrecorded thereon a clock pulse train corresponding to a single wordstorage area, a plurality of readout :hea-ds mounted adjacent saidsecond storage means and spaced round said second storage means at wordintervals, word selecting means for rendering operative one of saidread-out heads, gating means for all said transducing heads, and meanscontrolled by the pulses read out by said one of said read-out heads foropening said gating means to render said one of said transducing headseffective only during the passage of the selected word storage area.

3. Data storage apparatus comprising a multi-track, multi-word rotatablefirst magnetic storage means having a plurality of parallel data tracks,each track containing a plurality of successive Word storage areas, atransducing head for each said data track for serially transducingsignals corresponding to said successive word storage areas on therespective tracks, track selecting means for rendering operative one ofsaid transducing heads, second magnetic storage means synchronouslyrotatable with said first storage means and having recorded thereon aplurality of serial clock pulse trains each corresponding to a singleword storage area positionally arranged in a single clock track inaccordance with a predetermined code, a plurality of read-out headslocated in co-operative relation to said track and in spaced relation toone another, first and second control means, second selecting means forselectively connecting at least some of said read-out heads to saidfirst control means according to the word position to be selected andfor connecting the remaining heads to said second control means,read-out means controlled jointly by said first and second control meansfor reading out a clock pulse train in a time position corresponding tosaid selected word position, gating means for said transducing heads,and means controlled by said readout means for opening said gating meansto render said one of said transducing heads eifective only at the timewhen the selected word position passes said one of said transducingheads.

4. Data storage apparatus as claimed in claim 2, in which said trackselecting means and said word selecting means each comprise a switchingmatrix.

5. Data storage apparatus as claimed in claim 3, in'

which said track selecting means and said second selecting means eachcomprise a switching matrix.

6. Data storage apparatus including a rotatable magnetic storage memberwith a data storage track providing a plurality of word storage areas; atransducing head aligned with said data track; signal gating meansconnected to the transducing head; a clock pulse track with clock pulsesignals recorded therein; a plurality of clock pulse reading headsaligned with the clock pulse track and spaced apart along said track atequal intervals; and a switching network with a plurality of inputlines, one connected to each clock pulse reading head, a single outputline connected to said signal gating vmeans, and a pluralityjof controllines, the switching network being responsive to different word areaselecting combinations of potentials applied to the con trol lines toprovide connections between the output line and different selected onesof theinput lines, suchthat for each combination of control potentials agroup of clock pulses corresponding to a different one of said data wordareas appears on said output line, said gatf ing means being responsiveto the output clock pulse group to render the transducing head eifectiveduring the passage of the selected word area.

7. Data storage apparatus including a rotatable magnetic storage memberwith a plurality of data storage tracks, each providing a plurality ofword storage areas; a transducing head cooperating with each data track;a first switching network having an individual input line connected toeach transducing head, a single output line, and a plurality of controllines, the switching network being responsive to potentials applied tosaid control lines to connect a selected one of said input lines to theoutput line; a clock pulse track on said member with a single group ofclock pulse signals corresponding to a data word recorded therein; aplurality of clock pulse reading heads spaced apart at equal in tervalsalong the clock pulse track and cooperating therewith to generate atrain of clock pulse signals corresponding to each word position in adata storage track; a second ing heads, a single output line, and aplurality of cone trol lines, said second switching network beingrespon-f sive to potentials applied to said control lines to connect aselected one of said input lines to said output line; and a signalgating circuit connected to both said output lines.

8. Data storage apparatus including a rotatable magnetic storage drumwith a plurality of data storage tracks, each providing a plurality ofword storage areas; a transducing head cooperating with each data track;a first switching network having an individual input line for eachtransducing head, a single output line, and a plurality of controllines, the switching network being responsive to different combinationsof potentials applied to the control lines to connect different ones ofthe input lines to the output line; a plurality of clock pulse readingheads spaced apart at equal intervals along a clock pulse track on saidstorage drum, the clock pulse track having a plurality of groups ofclock pulses recorded therein, and so arranged that a unique combinationof reading heads are reading groups of clock pulses for each differentdata word area of a data track; a second switching network having aninput line for each said reading head, a single output line and aplurality of control lines, said second switching network beingresponsive to a selected one of a number of different combinations ofpotentials respectively uniquely representing different word storageareas of a track, applied to said control lines to pass that group oficlock pulses related to the word storage area represented by theselected combination to said output line;

and a signal gating circuit connected to both said output lines andopened by signals carried thereby.

9. Data storage apparatus including a rotatable magnetic storage memberwith a data storage track providing a plurality of word storage areas; atransducing head cooperating with each of the storage areas insuccession; signal gating means for the transducing head having a datatransmission line; a clock pulse track on said storage member dividedinto word areas corresponding to said word storage areas, said clockpulse track carrying clock pulses recorded thereon according to apredetermined pattern; a plurality of reading heads spaced apart at wordintervals along the clock pulse track and cooperating with the recordedclock pulse signals according to a predetermined code to generate groupsswitching network having an individual input line connected to each ofsaid clock pulse readof clock pulses corresponding to the word storageareas; a group of control lines; a static switching netvork connected tosaid group of control lines and having an output line, said networkbeingresponsive to address signals representing a required word storage areaapplied 'over the control lines to pass a selected group of clock pulsescorresponding to only the required word storage area over, said outputline; and means connecting said output line to said signal gating means,the

signal gating means being opened by the selected clock pulse group torender the transducing head operative to transfer data between the datatransmission line and that word storage area represented by the addresssignals.

References Cited in the file of this patent I UNITED STATES PATENTS2,771,595 Hendrickson et a1. Nov. 20, 1956

